Spring may come earlier to North American forests, increasing uptake of carbon dioxideTrees in the con ­ti ­nen ­tal U.S. could send out new spring leaves up to 17 days ear ­lier in the com ­ing cen ­tury than they did before global tem ­per ­a ­tures started to rise accord ­ing to a new study by Prince ­ton Uni ­ver ­sity researchers. These climate-driven changes could lead to changes in the com ­po ­si ­tion of north ­east ­ern forests and give a boost to their abil ­ity to take up car ­bon dioxide.Trees play an impor ­tant role in tak ­ing up car ­bon diox ­ide from the atmos ­phere so researchers led by David Med ­vigy assis ­tant pro ­fes ­sor in Princeton's depart ­ment of geo ­sciences wanted to eval ­u ­ate pre ­dic ­tions of spring bud ­burst -- when decid ­u ­ous trees push out new growth after months of win ­ter dor ­mancy -- from mod ­els that pre ­dict how car ­bon emis ­sions will impact global temperatures.The date of bud ­burst affects how much car ­bon diox ­ide is taken up each year yet most cli ­mate mod ­els have used overly sim ­plis ­tic schemes for rep ­re ­sent ­ing spring bud ­burst mod ­el ­ing for exam ­ple a sin ­gle species of tree to rep ­re ­sent all the trees in a geo ­graphic region.In 2012 the Prince ­ton team pub ­lished a new model that relied on warm ­ing tem ­per ­a ­tures and the wan ­ing num ­ber of cold days to pre ­dict spring bud ­burst. The model which was pub ­lished in the Jour ­nal of Geo ­phys ­i ­cal Research proved accu ­rate when com ­pared to data on actual bud ­burst in the north ­east ­ern United States.In the cur ­rent paper pub ­lished online in Geo ­phys ­i ­cal Research Let ­ters Med ­vigy and his col ­leagues tested the model against a broader set of obser ­va ­tions col ­lected by the USA National Phe ­nol ­ogy Net ­work a nation-wide tree ecol ­ogy mon ­i ­tor ­ing net ­work con ­sist ­ing of fed ­eral agen ­cies edu ­ca ­tional insti ­tu ­tions and cit ­i ­zen sci ­en ­tists. The team incor ­po ­rated the 2012 model into pre ­dic ­tions of future bud ­burst based on four pos ­si ­ble cli ­mate sce ­nar ­ios used in plan ­ning exer ­cises by the Inter ­gov ­ern ­men ­tal Panel on Cli ­mate Change.The researchers included Su-Jong Jeong a post ­doc ­toral research asso ­ciate in Geo ­sciences along with Elena Shevli ­akova a senior cli ­mate mod ­eler and Sergey Maly ­shev a pro ­fes ­sional spe ­cial ­ist both in the Depart ­ment of Ecol ­ogy and Evo ­lu ­tion ­ary Biol ­ogy and asso ­ci ­ated with the U.S. National Oceanic and Atmos ­pheric Administration's Geo ­phys ­i ­cal Fluid Dynam ­ics Laboratory.The team esti ­mated that com ­pared to the late 20th cen ­tury red maple bud ­burst will occur 8 to 40 days ear ­lier depend ­ing on the part of the coun ­try by the year 2100. They found that the north ­ern parts of the United States will have more pro ­nounced changes than the south ­ern parts with the largest changes occur ­ring in Maine New York Michi ­gan and Wisconsin.The researchers also eval ­u ­ated how warm ­ing tem ­per ­a ­tures could affect the bud ­burst date of dif ­fer ­ent species of tree. They found that bud ­burst shifted to ear ­lier in the year in both early-budding trees such as com ­mon aspen (Pop ­u ­lus tremu ­loides) and late-budding trees such as red maple (Acer rubrum) but that the effect was greater in the late-budding trees and that over time the dif ­fer ­ences in bud ­ding dates narrowed.The researchers noted that early bud ­burst may give decid ­u ­ous trees such as oaks and maples a com ­pet ­i ­tive advan ­tage over ever ­green trees such as pines and hem ­locks. With decid ­u ­ous trees grow ­ing for longer peri ­ods of the year they may begin to out ­strip growth of ever ­greens lead ­ing to last ­ing changes in for ­est make-up.The researchers fur ­ther pre ­dicted that warm ­ing will trig ­ger a speed-up of the spring green ­wave or bud ­burst that moves from south to north across the con ­ti ­nent dur ­ing the spring.The find ­ing is also inter ­est ­ing from the stand ­point of future changes in spring ­time weather said Med ­vigy because bud ­burst causes an abrupt change in how quickly energy water and pol ­lu ­tants are exchanged between the land and the atmos ­phere. Once the leaves come out energy from the sun is increas ­ingly used to evap ­o ­rate water from the leaves rather than to heat up the sur ­face. This can lead to changes in daily tem ­per ­a ­ture ranges sur ­face humid ­ity stream ­flow and even nutri ­ent loss from ecosys ­tems accord ­ing to Medvigy.Story Source:The above story is based on materials provided by Princeton  University. The original article was written by Cather ­ine Zan ­donella. Note: Materials may be edited for content and length.Journal References: